In this contribution we studied the thermal behavior of azidoarenes and azidohetarenes with and without reactive ortho-substituents to get insights in the thermal properties of these compounds which are interesting and important for thermal reactions.
By means of differentialscanningcalorimetry (DSC) we obtained besides melting points (which are in many cases of interest because the purity can be better determined than with chromatographic methods) the temperature areas for reaction or decomposition . This information is very valuable because it allows the synthetic chemist to plan the reaction conditions (e.g. to select suitable solvents and reaction temperatures which are high enough for a quick reaction, but below subsequent decomposition or rearrangement temperatures). Integration of the reaction and decomposition peak area gives information about the reaction enthalpy which in turn is a very important safety information. Together with the temperature it shows if and at which temperature a particular substance is an
Polymorphic Characterization of DifferentialScanningCalorimetry
Analytical techniques, such as DSC have proven suitable for the analysis and quantification of polymorphic mixtures and stability of API's and purity is tested using DSC as a routine practice in most of the R&D centre's and API units in most of the reputed companies.
Thermal analysis by differentialscanningcalorimetry (DSC)
Into an aluminum pan, an approximately of 9 mg of each oil sample was accurately weighed using an analytical balance with a sensitivity of 0.01 mg, and sealed into place. Thermal analyses were carried out using a DSC 823e Mettler Toledo instrument equipped with a sample robot (Julabo FT400 intracooler). The instrument was equipped with STARe excellence software for data interpretation. For the instrument calibration, indium and n-dodecane were used. The reference used was an empty covered aluminum pan of the same size as used in the samples. The samples were subjected to the following programmed temperature ramp, namely: 60 o C isotherm for 5 min, cooled at 5 o C/min to -60 o C and helard for 5 min. It was subsequently heated from -60 to 60 o C at 5 o C/
Isothermal DifferentialScanningCalorimetry (DSC) was used to study the crys- tallization kinetics of freeze-dried samples of lactose and sucrose at several tem- peratures between Tg and Tm. The sample was rapidly heated to the required temperature. After subtraction of an induction time, the Avrami equation was used to model the data and a Lauritzen-Hoffman like expression used to fit the derived rates of crystallization over the temperature range Tg<T<Tm. For both sugars the maximum rate of crystallization occurred at a temperature slightly higher than the midpoint of Tg and Tm. Crystallization rates were higher for lactose than sucrose. This could be explained by simple changes in Tg and Tm which could be accounted for by differences in moisture content.
To investigate and analyze the conditions that cause the failure, data of failed coatings must be collected, including the coating types, application procedures, service history and environment, and physical evidence. The data is used to determine why, how, when and where a failure may occur .
Therefore, in this paper, a field test was first conducted to determine the environment delaminating coatings, and then an electrochemical test and differentialscanningcalorimetry (DSC) were used to explore the causes of delamination. Understanding the causes of failure is necessary to prevent future coating failures
Abstract. DifferentialScanningCalorimetry (DSC) is a thermal analysis technique that measures the energy absorbed or released by a sample as a function of temperature or time. DSC has wide application for analysis of solid state reactions and solid-liquid reactions in many different materials. In recent years, DSC has been applied to analyze materials and alloys processed through Severe Plastic Deformation (SPD). The basic principle of SPD processing is that a very high strain is introduced into materials which achieve significant grain refinement and improve properties of materials. This review paper presents some recent examples of the applications of DSC for materials subjected to SPD, especially by Equal-Channel Angular Pressing and High-Pressure Torsion.
Differentialscanningcalorimetry (DSC) provides easy screening for thermal hazard evaluation. Here, we investigate the difference between using glass and stainless-steel vessels on the DSC measurement of exothermic decomposition energy (Q DSC ) for 41 chemical substances (containing nitro, halogen, peroxide, and sulfur groups, and hydrazine bonds). Two borosilicate glass vessels (ca- pillary and ampule) and one stainless-steel vessel were used. All Q DSC values obtained were investigated with reference to the permissible fluctuation range specified by the ASTM (American Society for Testing and Materials) interna- tional Both glass vessels produced very similar Q DSC values, despite different sample scales. The Q DSC values obtained with the glass vessels were generally roughly within the variation tolerance range of the stainless-steel vessel. Nota- ble exceptions were halogen- or sulfur-containing compounds; these exhibited smaller Q DSC values with glass vessels in almost all cases. We will investigate whether certain structures in compounds react with stainless steel. The vessel material choice is crucial in evaluating the true reactivity of a substance.
Crystallization kinetics of amorphous Fe 76 Tm 4 B 20 alloyhas been studied using DifferentialScanningCalorimetry (DSC). Calculation of activation energy(E a ) and frequency factor (k 0 ) of amorphous Fe 76 Tm 4 B 20 alloy has been doneusing Kissinger, Matusita-Sakka and Augis-Bennet methods.Using. The average value of activation energy (E a ) of crystallization is found to be equal to 430.85kJ/mol. Similarly, the Frequency factor(k 0 ) is calculated using Kissinger and Augis-Bennet methods which is found to be 5.39 x10 17 sec -1 , and 2.51 x10 19 sec -1 , respectively.It can be concluded that the Kissinger, Matusita-Sakka and Augis-Bennet relations are applicable to calculate the activation energy and frequency factor to explain the thermal stability of the sample.
Kazan (Volga Region) Federal University, Kazan, Russia
The formation of solid dispersions is one of the methods for drug hydrophilization. The data obtained by low temperature differentialscanningcalorimetry (DSC) has shown an opportunity to formation of solid dispersions of a hydrophobic drug – phenacetin with a biocompatible polymer – polyethylene glycol. It was established that in case of polymer:phenacetin 5-10:1 ratios the crystalline phase of the drug is not formed, while in case of 1-4:1 ratios the pharmacological component shows features of a separate phase and does not form a solid dispersion. The observed exo-effects on DSC curves of the mixtures of polymer:phenacetin with ratios of 1-2:1 and 7-10:1 are related to low-temperature crystallization of polymer. Optimal polymer:drug ratio is 5-6:1. At these ratios phenacetin completely dissolved in the polyethylene glycol phase and the quasi-stationary state caused amorphous part in solid dispersion is not observed. This together with absence of polymer plasticization by phenacetin may facilitate the release of the drug from the composite in hydrophilic media. The melting temperature of solid dispersions does not exceed 35.2 ° С allowing their use as capsular drugs, ointments and suppositories.
before reaching its melting point. In fact, at a scanning rate of 1 °C/min only the exothermic peak appeared in the thermogram, suggesting complete decomposition prior to melting under the dynamic flow of synthetic air. At 126°C the drug were found to produce a sharp endothermic peak characterizing its melting point. 18 The difficulty of formulating cephalosporins as freeze-dried products lies in the freezing characteristics of their aqueous solutions. The thermal characteristics of aqueous solutions of several cephalosporins were examined by DifferentialScanningCalorimetry (DSC) during freezing and warming cycles. It was found that DSC studies of cephalosporin solutions show that they typically do not crystallize during freezing and do not form eutectics. The ones examined also do not go into metastable states during freezing. In addition, the physical state of the “frozen” matrix (in terms of presence or absence of a liquid phase) cannot be clearly ascertained by DSC because the compounds do not form eutectics with water. Therefore, in the determination of parameters to be employed in the design of an optimum lyophilization cycle for compounds like these, DSC may be of limited use. The compound did not crystallize from such solutions and do not form eutectic mixtures with water. Also, freezing did not produce any detectable metastable states of the solutes. Therefore, in the determination of parameters to be used in designing an optimum freeze-drying cycle for compounds such as these, DSC may be of limited use. 19 It is very important to characterize the freeze-dried matrix and to investigate the conservation of the nanoparticle properties. Furthermore such characterization may validate the applied conditions of the process and the optimized formulation. During storage, freeze-
Calorimetric studies reveal information about the depen- dence of the thermal behavior of a material on molecular mobility, which affects the microstructure and chemical reactions of the material. Differentialscanningcalorimetry (DSC) measures the thermal behavior and transitions of polymers during heating and cooling. It is especially important for measuring and controlling the glass transition temperatures of industrial polymers in the conditions in which they are used. This is significant because most polymeric materials have amorphous structures and their microstructures gradually change below the glass transition temperature due to enthalpy and volume relaxations. These changes to their microstructures affect their physical and mechanical properties.
This study measured the specific heat capacity of Phyllostachys edulis (Moso Bamboo) in three directions of the cylindrical coordinate system. The specific heat capacity measurement was conducted by the differentialscanningcalorimetry (DSC). Results from both internode and node parts of the bamboo culms were presented and compared in this study. Typical results at 25 ° C were collected for an overall comparison of total specific heat capacity data. A major finding was that the specific heat capacity of the bamboo solid phase increased with the temperature.
Therefore it is important to understand interaction of ligands to prevent the formation of amyloid fibrils. The purpose of the present study was to characterize AChE structure using differentialscanningcalorimetry (DSC), fluorescent probe and docking methods. Immobilization of AChE was carried out on porous silica matrix. Fluorescence of free and immobilized form of AChE was measured by a spectrofluorometer at 435 nm excitation wavelength .Calorimetric measurements were carried out on a differentialscanning calorimeter. AChE–ligand docking Version Lig plot was used for docking studies. Based on our data, thioflavin T (Th-T) binding to the peripheral site of AChE, increased its fluorescence in a dose-dependent manner. DSC showed that immobilized AChE form is probably more stable structurally than its free form. Protein docking study revealed that AChE interacts through different regions with matrix, and each of these interactions have its own binding energy. A comparison between DSC, fluorescence spectroscopy and docking results revealed excellent agreement between them.
Therefore, measuring the ¡/£ transformation latent heat in a magnetic ﬁeld is important. Beyond improving the basic understanding of phase transformations, these measurements will enhance the accuracy of thermodynamically based predictions of phase stability in a magnetic ﬁeld. Thus, this study aims to reveal the effect of a magnetic ﬁeld on the latent heat and the transformation entropy in Fe and FeCo binary alloys using a specially designed differentialscanningcalorimetry (DSC) system equipped with a superconducting magnetic-ﬁeld heating system. We report on changes in the entropy of the ¡/£ phase transformation in Fe and FeCo alloys under a magnetic ﬁeld; to our knowledge this effect has not been previously reported.
Interactions in interesterified palm and palm kernel oils mixtures. II – Microscopy and DifferentialScanningCalorimetry.
Palm oil (PO) and palm kernel oil (PKO) compositions (100/0, 80/20, 60/40, 50/50, 40/60, 20/80 and 0/100) were interesterified in laboratory scale under predetermined conditions (0.4% sodium metoxide, 20 minutes, 100 o C). The fourteen samples, before and after interesterification, were characterized by Polarized Light Microscopy and DifferentialScanningCalorimetry (DSC). Results showed the effect of various factors on the form and width of crystals. The mean area of crystals revealed the increase of crystals when PKO was added, with values varying from 2.7 x 10 3 µm 2 to PO and 1.8 x 10 6 µm 2 to PKO. After interesterification, the
Figure 4. The curing rate corresponding to the crosslinking of a partially bio‐based epoxy resin as a function of the conversion, , for different heating rates, β.
One of the most important parameters of a kinetic study is the apparent activation energy, E a . As indicated previously, the Kissinger method allows for estimating a single value of E a for the curing process by using Equation (15). One important condition needed to apply the Kissinger method is that the conversion at the maximum reaction rate, denoted as 𝛼 , must be very similar for all the heating rates. As can be observed in Table 3, 𝛼 p showed an average value of 0.41 ± 0.01, and all the values corresponding to different heating rates are quite similar. Therefore, in a first instance, the Kissinger method could be applied. Figure 5 shows the typical plot representation of the Kissinger method, showing good linear fitting. In particular, the E a obtained from the slope was 57.3 ± 3.1 kJ mol −1 . As it has been indicated previously, the peak width of the curing rate is also representative for a single step process. For this reason, a plot of ln t FWHM versus 1/T p has been used to check this. The experimental data and the corresponding linear fit can be seen in Figure 6. The E a value obtained from the peak width at half maximum was 57.4 ± 3.1 kJ mol −1 . This value is in good agreement with that obtained using the Kissinger method, thus suggesting the curing process took place in a single step process. The reactions that take place during a polymerization process could be quite complex due to the polymer chemical structure, diffusion phenomena, crosslinking density, monomer functionality, and chain mobility, among others . Despite this, the overall process for this particular system, analysed using differentialscanningcalorimetry, appears to be a single step process (quite homogeneous and symmetric exothermic peak). Therefore, although there could be different activation energies for different processes occurring in the crosslinking, by using DSC, it is possible to obtain a unique “apparent” activation energy, E a , representative for all the processes that are overlapped.
Differentialscanningcalorimetry (DSC) was used to determine the thermal events associated with freezing and melting of the cysts of the potato-cyst nematode Globodera rostochiensis. There were no thermal events during the cooling of dry cysts from 5 to 2 60 ˚C and warming back to 5 ˚C, indicating the absence of water freezing in the dry cysts. During heating of dry cysts from 5 to 80 ˚C, two overlapping endothermic events were observed at 55 ˚C, indicating the irreversible destruction of the permeability barrier of the eggshell by the melting of the lipids which constitute the lipid layer.
Received: 21 December 2017; Published online: 18 October 2019
Native starch was extracted from nine germplasm collections of Araucaria angustifolia seeds in aqueous medium and they were characterized by Pasting Properties (RVA), X-ray Powder Diffrac- tometry (XRD) and Scanning Electron Microscopy (SEM). The gelatinization process of each sample was evaluated at different ratios of starch:water by DifferentialScanningCalorimetry (DSC). A slight displacement in the gelatinization curves was observed for the pinh˜ ao starches prepared with different amounts of water. With an increase in water content, most of the samples presented a decrease in the peak, the conclusion temperatures, and the range of gelatinization temperatures, while the enthalpy did not follow a standard behavior. A displacement or a narrowing of the gelatinization temperature range occurred with increasing water content. Pinh˜ ao starch showed pasting temperature in the range of 60-67 o C and there were differences in the pasting properties and degree of relative crystallinity between the analyzed samples. The C-type diffraction pattern was found for all the samples and the morphology of starch granules was similar, with oval and round shapes. Therefore, different character- istics were found among starches from nine germplasm collections, encouraging the protection of the biological diversity of selected species, aiming at future applications.
Furthermore, in-situ X-ray and neutron diffraction measure- ments 5–8) have shown that the space group of the α and β phases is P6/mmm and that of the γ phase is P6 3 mc. However, little is known about the kinetics of the transformation be- tween these phases in the processes of hydrogenation and de- hydrogenation. To study the phase transformation of the hy- drides, the pressure differentialscanningcalorimetry (PDSC) is suitable, because the phase transformations can be easily found out by their endothermic and exothermic reactions in the calorimetry. Furthermore, the activation energy for the phase transformation can be determined by Ozawa’s method 9) in the measurements of DSC with different heating and cool- ing rates.
Plastics — Fast differentialscanningcalorimetry (FSC) — Chip calorimetry
This document specifies the characteristics of non-adiabatic fast differentialscanning calorimeters, also covered by the general abbreviation FSC having an open specimen geometry in which specimens are placed directly onto active measurement areas of chip sensors based on Micro-Electro-Mechanical Systems (MEMS) membrane technology, without encapsulation in closed crucibles and ovens.